1. Field of the Invention
The present invention relates generally to optical fibers, and particularly to coatings applied to the optical fiber.
2. Technical Background
Optical fibers have acquired an increasingly important role in the field of communications, frequently replacing existing copper wires. This trend has had a significant impact in the local area networks (i.e., for fiber-to-home uses), which has seen a vast increase in the usage of optical fibers. Further increases in the use of optical fibers in local loop telephone and cable TV service are expected as local fiber networks are established to deliver ever greater volumes of information in the form of data, audio, and video signals to residential and commercial users. In addition, use of optical fibers in home and commercial business environments for internal data, voice, and video communications has begun and is expected to increase.
Optical fibers typically contain a glass core, a glass cladding, and at least two coatings, e.g., a primary (or inner) coating and a secondary (or outer) coating. The primary coating is applied directly to the glass fiber and, when cured forms a soft, elastic, and compliant material which encapsulates the glass fiber. The primary coating serves as a buffer to cushion and protect the glass fiber core when the fiber is bent, cabled, or spooled. The secondary coating is applied over the primary coating and functions as a tough, protective outer layer that prevents damage to the glass fiber during processing and use. The optical fibers may also include an ink as an outer most layer to assist in identifying different optical fibers included in a fiber optic ribbon or cable.
In the past, the ink layer has exhibited poor adherence to the outer coating layer. The ink layer at times may delaminate from the adjacent coating layer. There exists a need to improve the adherence between the ink layer and the outer most coating layer and still maintain the ink pigment evenly dispersed throughout the ink.
One aspect of the present invention is an optical fiber coating composition. The composition is a UV curable composition which includes a coupling agent devoid of any Si containing compound. The cured composition has a Young""s modulus of at least about 50 MPa.
In another aspect, the present invention relates to an optical fiber coating. The coating is a UV curable coating which includes a coupling agent devoid of any Si containing compound. The coating is located not less than about 5 microns away from an outer surface of the glass fiber.
In a further aspect, the present invention relates to an optical fiber coating. The coating is a UV curable coating which comprises a coupling agent devoid of any Si containing compound. The cured coating has a percent change in tensile strength of no more than about 10% after the cured coating has been exposed to about 85% relative humidity at 85xc2x0 C. for at least about 14 days. Preferably the coating has a percent change in Young""s modulus of no more than about 10% after the cured coating has been exposed to about 85% relative humidity at 85xc2x0 C. for at least about 14 days. It is also preferred that the coating has a percent change in Secant modulus of no more than about 15% after the cured coating has been exposed to about 85% relative humidity at 85xc2x0 C. for at least about 14 days.
The use of the aforementioned coupling agent in an ink will result in the advantages of the ink having better adhesion to the secondary coating for at least the reason that the ink is reactive. Inks which include the inventive coupling agent have also exhibited the advantage of decreased settling rates than that of inks without the inventive coupling agent.
Optical fiber coatings that include the inventive coupling agent have exhibited the advantage of enhanced physical properties. Optical fiber coatings which included the inventive coupling agent have demonstrated the advantage of exhibiting less of a change in tensile strength, Young""s Modulus, and Secant Modulus after the coating was exposed to a wet environment.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.